The present invention relates to a vehicle seat and more particularly, relates to a vehicle seat intended for use in a motor vehicle such as a motor car.
It has been appreciated that if a motor vehicle, such as a motor car, is involved in a rear-end collision or rear impactxe2x80x94that is to say if a following vehicle runs into the back of the carxe2x80x94the occupants of the struck car often suffer from neck injuries.
It is to be understood that during a rear-end collision of this type, the vehicle that is struck is subjected to a forward acceleration. This imparts a forward acceleration to the seats of the vehicle. The squab and the back of each occupied seat engage the posterior and torso of the occupant of the seat and impart a substantial acceleration to the posterior and torso of the occupant. However, no corresponding acceleration is immediately imparted to the head of the occupant. The head is a part of the body that has substantial mass, and consequently the head has substantial inertia.
Thus, while the posterior and torso of the occupant of the vehicle are accelerated forwardly as a result of the rear-end collision, the head of the occupant of the vehicle initially remains stationary. This causes the neck initially to adopt a xe2x80x9cSxe2x80x9d-shaped configuration as the lower part of the neck moves forwardly, while remaining vertical, and the upper part of the neck remains in its initial position. Subsequently, the head begins to rotate, and the neck then occupies a curved configuration. The head subsequently moves forwardly. Research has shown that xe2x80x9cwhiplashxe2x80x9d injuries may occur when the neck adopts the xe2x80x9cSxe2x80x9d-shaped configuration, if the head is moving, relative to the torso, at a substantial speed.
The present invention seeks to provide an improved vehicle seat in which the risk of xe2x80x9cwhiplashxe2x80x9d injuries occurring to the occupant of the seat during a rear-end collision are reduced.
According to this invention there is provided a vehicle seat, the seat comprising a squab and a back, the back being mounted for pivotal movement relative to the squab of the seat incorporating energy absorbing force limiting components to absorb energy as the back of the seat moves rearwardly when subjected to a force from the torso of an occupant of the seat, if a vehicle in which the seat is mounted is involved in a rear impact, the energy absorbing force limiting components providing a first resistive force resisting the pivotal movement during a first predetermined pivotal movement, and a second resistive force during a second subsequent pivotal movement, the resistive force provided during the first pivotal movement being dependent upon the energy of the rear impact.
Preferably the energy absorbing force limiting components comprises elements to provide the first resistive force comprising an energy absorbing force limiting device and a dampening spring.
Conveniently the energy absorbing force limiting device and the dampening spring are connected in series between the back of the seat and an element mounted on the squab of the seat.
Advantageously the dampening spring comprises a spring connected in parallel with a fluid-filled cylinder containing a double acting piston, the opposed ends of the cylinder being inter-connected by a parallel connection of a non-return valve and a constriction.
Preferably the energy absorbing force limiting components comprise a framework present within the back of the set adapted to deform when subjected to a predetermined force.
Advantageously the energy absorbing force limiting components comprise an energy absorbing force limiter adapted to provide said second resistive force during the second subsequent pivotal movement.
Conveniently the back of the seat is mounted for pivotal movement between predetermined limits relative to a support, the support being pivotally mounted to the squab of the seat, the energy absorbing force limiter providing the second resistive force during the second subsequent pivotal movement being adapted to provide the resistive support on pivotal movement of said support.
In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: